1. Field of the Invention
The present invention relates to a securing device for a light interception frame provided in a lens barrel.
2. Description of the Related Art
Generally, a light interception frame is provided in a lens barrel to remove extraneous light, such as stray light. Such stray light has adverse effects on the exposure of a photographic image. FIG. 11 shows, by way of example, a known light interception frame which is secured to a rear end of a lens frame which supports a predetermined lens group. In FIG. 11, lenses L10 and L20 are supported at front and rear ends of a lens support cylinder 100, and a light interception frame 200 is provided adjacent to the rear end face of the lens L20.
The lens support cylinder 100 is provided on its outer peripheral surface with a plurality of engagement pawls 101 that extend in the radial and outward direction. The light interception frame 200 is provided on its periphery with a plurality of engagement legs 201 corresponding to the engagement pawls 101, which extend in the forward direction (left direction in FIG. 11). Note that in FIG. 11, only one engagement pawl 101 and only one engagement leg 201 corresponding thereto are shown. The engagement legs 201 are each provided with an engagement hole 202, so that when the engagement pawls 101 are engaged in the corresponding engagement holes 202, the light interception frame 200 is secured to the lens support cylinder 100.
In this arrangement, it is necessary to mount the light interception frame 200 to the lens support cylinder 100 in such a way that the outer peripheral portion of a light interception plate 203 of the light interception frame 200 is in elastic contact with the end face (rear end face) 102 of the lens support cylinder 100, otherwise, the light interception frame 200 could slip off from the lens support cylinder 100. Namely, in FIG. 11, if the dimensional value D1 (distance between the light interception plate 203 and the front ends of the engagement holes 202) is identical to or greater than the dimensional value D2 (distance between the end face 102 of the lens support cylinder 100 and the front ends of the engagement holes 202), i.e., D1xe2x89xa7D2, the light interception frame can easily slip off. To prevent this, D1 must be smaller than D2 (D1 less than D2).
However, in the case where the lens L20 is fitted in and secured to the lens support cylinder 100 by thermally caulking the lens support cylinder 100 at the rear end thereof (while applying a heated metal to the lens support cylinder to thereby fuse the same), there is a possibility that the shape of the end face 102 is not identical, and thus the dimensional value D2 is irregular. In view of this possibility, it is necessary to strictly regulate (manage) the shape of the end face 102 which determines the dimensional value D2 so as to meet the requirement that D2 is always larger than D1.
It is an object of the present invention to provide a securing device for a light interception frame in which the light interception frame can always be reliably mounted to the lens frame without need of strict regulation of the dimension and shape of the portion of the lens frame to which the light interception frame is mounted.
To achieve the object of the present invention, according to the present invention, a securing device is provided for securing a light interception frame made of a resilient material to an end face of a lens frame which holds a lens. The lens frame is provided on the peripheral surface thereof with a plurality of engagement projections which extend in a direction substantially perpendicular to an optical axis of the lens, and a plurality of engagement surfaces which are located between the engagement projections and lie in a plane substantially perpendicular to the lens axis. The light interception frame includes a light interception plate portion that has an opening through which light can pass and that lies in a plane substantially perpendicular to the lens axis, a plurality of engagement legs that extend from the outer peripheral edge of the light interception plate portion and that engage with the corresponding engagement projections, and a plurality of engagement pieces that extend from the outer peripheral edge of the light interception plate portion and abut against the corresponding engagement surfaces. The positional relationship between the plurality of engagement projections and the plurality of engagement legs, and the positional relationship between the plurality of engagement surfaces and the plurality of engagement pieces are such that when the engagement pieces engage with the engagement surfaces in a free state of the light interception frame, no engagement of the engagement legs with the engagement projections occurs, and the engagement legs are engaged by the engagement projections by elastically deforming the light interception frame.
Preferably, the engagement legs are provided with engagement holes in which the corresponding engagement projections are engaged.
The lens held by the lens frame can be secured to the lens frame by thermally caulking the end face of the lens frame after the lens is fitted in the lens frame from the end face side. In such a case, the light interception frame is secured to the lens frame by the securing device, wherein the light interception plate portion is opposed to the end face of the lens frame that has been subject to the thermal caulking.
Preferably, the light interception plate portion is provided, on the end portions of the engagement legs which connect to the light interception plate portion, with cut-away portions so as to facilitate elastic deformation of the engagement legs.
According to another aspect of the present invention, a light intercepting device for a lens is provided, including a lens frame which holds a lens, the lens frame being provided on the peripheral surface thereof with a plurality of engagement projections which extend in a direction substantially perpendicular to an optical axis of the lens, and a plurality of engagement surfaces which are located between the engagement projections, the engagement surface lying in a plane substantially perpendicular to the lens axis; and a light interception frame made of a resilient material, the light interception frame being provided with a light interception plate portion that lies in a plane substantially perpendicular to the lens axis and has an opening through which light can pass, a plurality of engagement legs that extend from the outer peripheral edge of the light interception plate portion and engage with corresponding engagement projections, and a plurality of engagement pieces that extend from the outer peripheral edge of the light interception plate portion and abut against corresponding engagement surfaces. The light interception frame is secured to an end face of the lens frame so that the engagement legs are engaged by the engagement projections by elastically deforming the light interception frame when the engagement legs are engaged with the engagement projections.
Preferably, the engagement legs are provided with engagement holes in which the corresponding engagement projections are engaged.
The lens held by the lens frame can be secured to the lens frame by thermally caulking the end face of the lens frame after the lens is fitted in the lens frame from the end face side. In such a case, the light interception frame is secured to the lens frame, wherein the light interception plate portion is opposed to the end face of the lens frame that has been subject to the thermal caulking.
Preferably, the light interception plate portion is provided, on the end portions of the engagement legs which connect to the light interception plate portion, with cut-away portions so as to facilitate elastic deformation of the engagement legs.
According to another aspect of the present invention, a securing device is provided for securing a light interception frame made of a resilient material to an end face of a lens frame which holds a lens, including a plurality of engagement projections and a plurality of engagement surfaces provided on the peripheral surface of the lens frame, the plurality of engagement projections extending in a direction substantially perpendicular to an optical axis of the lens, and the plurality of engagement surfaces being located between the engagement projections and lying in a plane substantially perpendicular to the lens axis; and a plurality of engagement legs and a plurality of engagement pieces provided on the light interception frame having a light interception plate portion, the plurality of engagement legs extending from the outer peripheral edge of the light interception plate portion and engaging with corresponding engagement projections, the plurality of engagement pieces extending from the outer peripheral edge of the light interception plate portion and abutting against corresponding engagement surfaces; wherein the light interception plate portion lies in a plane substantially perpendicular to the lens axis and has an opening through which light can pass. The positional relationship between the plurality of engagement projections and the plurality of engagement legs, and the positional relationship between the plurality of engagement surfaces and the plurality of engagement pieces are such that when the engagement pieces engage with the engagement surfaces in a free state of the light interception frame, no engagement of the engagement legs with the engagement projections occurs, and the engagement legs are engaged by the engagement projections by elastically deforming the light interception frame.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2000-19918 (filed on Jan. 28, 2000) which is expressly incorporated herein by reference in its entirety.